The present invention relates to a method for the preparation of fine spherical particles of a silicone elastomer useful as an additive in thermoplastic and thermosetting resins for improving the impact strength of the resin, lubricity improver or anti-blocking agent in paints, filler in cosmetic preparations and so on.
Several proposals have been made in the prior art on a silicone elastomer composition loaded with fine particles of a silicone elastomer. For example, a heat-curable epoxy resin composition is disclosed in Japanese Patent Kokai No. 59-96122, according to which an epoxy resin is blended with a composition containing spherical particles of an organopolysiloxane elastomer cured by heating in the presence of an organic peroxide. The spherical particles of the silicone elastomer are obtained by spray-drying a curable organopolysiloxane composition at a temperature of 230.degree. to 300 .degree. C. This method has several problems and disadvantages. For example, the lower limit of the diameter of the thus obtained particles cannot be smaller than the diameter of the droplets of the curable organopolysiloxane composition formed by spraying so that the average particle diameter thereof can rarely be smaller than 100 .mu.m without subsequent pulverization. In addition, it is sometimes difficult to adequately control the curing velocity of the composition since the curing reaction must proceed during the period in which the droplets formed by spraying fall within the spray chamber.